A useful table of recommended sample
sizes for tests with 200 mm or 8” diameter
sieves is presented in Table 4
. Note that
the table gives sample sizes listed by
volume. Recommended sample weights in
grams can be determined by multiplying
the values in Column 3 and 4 by the bulk
density (grams per cubic centimeter) of the
material to be tested rounded out within a
reasonable tolerance. If the actual bulk
density of a certain material is not known,
they typical density factor for the most
nearly similar material listed in Table 5
may by used.
To perform the actual sieve analysis,
sieves should be chosen in a sequence as
described earlier. Use every sieve, every
other sieve, or every third sieve, etc.
between the desired size parameters. The
use of sieves in this sequential order will
allow for better data presentation and a
more meaningful analysis of the test
results. Care should also be taken in
selecting the proper sieves to avoid
overloading any sieve with an especially
large material peak. For example, a
specification may require 96% of the
sample be retained above a #50 mesh
sieve. The proper way to perform an
analysis of this nature is to use ’relief
screen’, that is, sieves in the 30, 35, 40
and 45 mesh ranges to remove some of
the burden from the critical cut point of 50
mesh. If the relief sieves are not used, the
particles of exactly 50 mesh size or slightly
larger may become wedged in or forced
through the sieve openings by the mass of
material resting above them. Large
concentrations of material on one sieve
reduce the opportunity for near sized
material to pass through the sieve resulting
in a larger portion of the material retained
on the test sieve. The sieve cut point
would be inaccurate and the sample would
not meet the specifications for the test.
The selected sieves should be
assembled with the coarsest sieve at the
top of the stack and the balance of the
stack in increasing magnitude of fineness
(increasing sieve numbers with smaller
openings). The stack should include a
1
With the inclusion of the new ASTM E 11-09 Standards
Table, this is now featured in Table 5.
2
With the inclusion of the new ASTM E 11-09 Standards
Table, this is now featured in Table 6.
cover on the top sieve and a pan below the
finest sieve. The sieve stack can be
shaken then rapped by hand or mounted in
a sieve shaker with a motorized or
electrostatic drive mechanism.
While many applications still use the hand-
shaken method for sieving, motor driven
shakers have proven to be much more
consistent, minimizing variations related to
operator procedures. In powder analysis
below the 100 mesh range, the sieve
shaker should be equipped with a device to
impart a shock wave to the sieve stack at
regular intervals. This hammer or rapping
device is necessary to reorient the particles
on the sieve and impart some shear forces
to near-sized particles blocking the sieve
openings.
Recommended Time Intervals
The duration of the sieving interval is
usually regulated by industry standards, or
by in-house control specifications.
Commonly, 10, 15 or 20 minute tests are
used as arbitrary sieving intervals. To
determine the best interval for a new
material, or to double check the accuracy
of existing specifications, the following
procedure can be used. Select the desired
sieves for the analysis. 1) Weigh up a
sample of the material to be tested and
introduce it to the complete sieve stack. 2)
Shake the sieve stack for a period of 5
minutes. 3) Weigh the residue in the pan
and calculate the percentage in relation to
the starting weight. 4) Reassemble the
stack and shake for one additional minute.
5) Repeat the weigh-up procedure and
calculate the percentage. If the
percentage of fines increased more than
1% between 5 minutes and 6 minutes,
reassemble the stack and shake for an
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